Diaphragm Hydrogen Compressor Market Size and Forecast 2021 - 2034, Global and Regional Share, Trend, and Growth Opportunity Analysis Report Coverage: By Type, End User, and Geography

List of Tables

The Diaphragm Hydrogen Compressor Market size was valued at US$ 363.53 million in 2025 and is expected to reach US$ 551.83 million by 2034; it is estimated to record a CAGR of 4.7% during 2026-2034.

Demand for oil and gas has increased across both developed and developing countries, driving higher levels of production activity along with greater investment and research and development efforts. For example, in January 2023, the CEO of the National Iranian Oil Company (NIOC) stated at a conference on enhanced recovery from oil and gas wells that the company had invested US$1 billion in developing the joint Sohrab field in Khuzestan Province. He also noted plans to collaborate with local firms to improve the efficiency of 600-700 underperforming wells. Similarly, in April 2022, China National Offshore Oil Corporation (CNOOC) reported the successful implementation of China's first large-scale offshore super-heavy thermal oil recovery development model. In April 2023, Oil and Natural Gas Corporation (ONGC) secured around US$7 billion in funding to support oil and gas production over the next three to four years. In Indonesia, the government has actively supported the growth of the Enhanced Oil Recovery (EOR) sector through policies and regulations encouraging adoption of EOR technologies. In September 2021, Indonesia's Energy Minister Arifin Tasrif outlined plans to raise production to 1 million barrels per day, supported by strategies such as optimizing existing reserves, accelerating EOR deployment, expanding exploration, and developing unconventional resources. Collectively, these developments are increasing demand for hydrogen compressors within the oil and gas sector, thereby supporting market growth.

At the same time, governments in the United States and Canada are advancing hydrogen as a central element of their long-term energy transition strategies. On June 5, 2023, the Biden-Harris Administration introduced the National Clean Hydrogen Strategy and Roadmap, establishing a framework to accelerate hydrogen production, distribution, storage, and end-use, while supporting goals of a carbon-free power sector by 2035 and net-zero emissions by 2050. Canada released its Hydrogen Strategy in December 2020, aiming to position itself as a global leader in low-carbon hydrogen production and export in line with its 2050 net-zero target. More recently, in August 2024, Canada's Minister of Energy and Natural Resources announced a US$9.14 million investment to advance clean hydrogen innovation, including funding for a University of British Columbia pilot project using pyrolysis technology and a hydrogen hybrid demonstration project by Enbridge Gas Inc. in Ontario. These initiatives are expected to strengthen hydrogen infrastructure and generate opportunities for compressor manufacturers. Overall, the North American diaphragm hydrogen compressor market is experiencing steady growth, supported by favorable policies, technological progress, and expanding adoption of hydrogen-based applications across industries.

In 2023, the United States ranked as the second-largest center for manufacturing and industrial output globally, after China. The manufacturing sector generated approximately US$2,900 billion and contributed over 12% to the country's GDP. To sustain and enhance this level of industrial growth, continued investment in hydrogen infrastructure expansion is essential, which is expected to drive demand for hydrogen compressors. Much of the existing infrastructure in the US is aging and requires modernization and capacity upgrades, particularly in sectors such as oil and gas, energy, refining, petrochemicals, and aviation. As investments increase to upgrade these industries, hydrogen demand as a transition fuel is also expected to rise. In addition, expanding upstream and downstream oil and gas operations, along with growing government-led power generation and transmission projects, are further supporting market growth. Hydrogen compressors are also widely used in energy storage systems in nuclear power facilities and industrial manufacturing applications.

The US government has committed around US$50 billion to developing a Clean Hydrogen Economy and plans to establish seven regional clean hydrogen hubs. Hydrogen compressors play a key role in electricity storage systems for nuclear power plants and industrial operations. In March 2022, the US Department of Energy announced US$750 million in funding for hydrogen production research and development to support clean hydrogen initiatives. This investment was later increased to US$1.5 billion in 2022 to help reduce the cost of clean hydrogen production, with additional support coming from private-sector initiatives such as Plug Power Inc.'s R&D programs.

In Canada, the government introduced a federal budget in April 2023 allocating approximately US$12.6 billion toward clean hydrogen investments from 2023 to 2035. According to the Canadian Association for Petroleum Producers, upstream oil and gas investments reached US$29.4 billion in 2023, recovering beyond pre-pandemic levels. Hydrogen compressors are used in oil and gas refineries for gas compression processes. The Fraser Institute notes that the oil and gas sector contributes about 8% to Canada's GDP and represents a major source of tax revenue, making it a key driver of national economic activity and employment.

Canada's stable economy, advanced infrastructure, and strong technology adoption further support its position as a favorable market for hydrogen technologies. The government continues to implement supportive policies aimed at strengthening domestic industrial production. As one of the world's leading oil and gas producers, Canada is home to roughly 1,000 exploration and production companies. According to the Canadian Centre for Energy Information, capital investment in the power sector reached US$80 billion in 2022, with oil and gas extraction accounting for US$31.9 billion of total energy sector spending. Increasing infrastructure investments in these sectors are expected to boost hydrogen adoption as a transition fuel, thereby driving demand for hydrogen fueling stations and supporting growth in the diaphragm hydrogen compressor market.

Atlas Copco AB; Fluitron, Inc.; Gardner Denver Nash, LLC; Burckhardt Compression AG; HAUG Sauer Kompressoren AG; Howden Group; NEUMAN & ESSER GROUP; Hydro-Pac, Inc.; Lenhardt & Wagner GmbH; PDC Machines Inc.; Sundyne; and Ariel Corporation are among the key diaphragm hydrogen compressor market players that are profiled in this market study.

The overall diaphragm hydrogen compressor market size has been derived using both primary and secondary sources. Exhaustive secondary research has been conducted using internal and external sources to obtain qualitative and quantitative information related to the diaphragm hydrogen compressor market size. The process also helps obtain an overview and forecast of the market with respect to all the market segments. Also, multiple primary interviews have been conducted with industry participants to validate the data and gain analytical insights. This process includes industry experts such as VPs, business development managers, market intelligence managers, and national sales managers, along with external consultants such as valuation experts, research analysts, and key opinion leaders, specializing in the diaphragm hydrogen compressor market.

Product Code: TIPRE00043153

1. Executive Summary

1.1 Analyst Market Outlook
1.2 Market Attractiveness

2. Diaphragm Hydrogen Compressor Market Landscape

2.1 Overview
2.2 Value Chain Analysis
2.3 Supply Chain Analysis
- 2.3.1 List of Manufacturers/Suppliers
- 2.3.2 List of Potential Customers (Upto 50)
2.4 Porter's Five Force Analysis
2.5 PEST Analysis
2.6 Impact of Artificial Intelligence (AI)
2.7 Sustainability and ESG Trends
2.8 Regulatory Framework

3. Competitive Landscape

3.1 Company Benchmarking by Key Players
3.2 Market Share Analysis, 2025 - By Key Players
3.3 Market Concentration

4. Diaphragm Hydrogen Compressor Market - Key Industry Dynamics

4.1 Market Drivers
- 4.1.1 Increased Adoption of Hydrogen Fuel Cell Vehicles
- 4.1.2 Investments Across the Oil & Gas Sector
- 4.1.3 Expansion of Industrial Production Activities
4.2 Market Restraints
- 4.2.1 High Recurring Cost in Maintenance
- 4.2.2 High Initial Capital Investment
- 4.2.3 Technical Challenges and Safety Concerns
4.3 Market Opportunities
- 4.3.1 Investments in Renewable Energy and Hydrogen Generation Projects Worldwide
- 4.3.2 Expansion of Hydrogen Refueling Infrastructure
- 4.3.3 Decarbonization of Hard-to-Abate Industries
4.4 Future Trends
- 4.4.1 Development of Advanced and Alternative Hydrogen Compression Technologies
- 4.4.2 Increasing Shift Toward Green Hydrogen
- 4.4.3 Integration of Digital and Smart Monitoring Technologies
4.5 Impact of Drivers and Restraints

5. Diaphragm Hydrogen Compressor Market - Global Market Analysis

5.1 Diaphragm Hydrogen Compressor Market Revenue (US$ Million), 2021-2034
5.2 Diaphragm Hydrogen Compressor Market Forecast and Analysis

6. Diaphragm Hydrogen Compressor Market Revenue Analysis - Type

6.1 Diaphragm Hydrogen Compressor Market Forecasts and Analysis by Type
- 6.1.1 Lubricated
  - 6.1.1.1 Overview
  - 6.1.1.2 Lubricated: Diaphragm Hydrogen Compressor Market - Revenue, 2021-2034 (US$ Million)
- 6.1.2 Oil-free
  - 6.1.2.1 Overview
  - 6.1.2.2 Oil-free: Diaphragm Hydrogen Compressor Market - Revenue, 2021-2034 (US$ Million)

7. Diaphragm Hydrogen Compressor Market Revenue Analysis - End User

7.1 Diaphragm Hydrogen Compressor Market Forecasts and Analysis by End User
- 7.1.1 Power Plants
  - 7.1.1.1 Overview
  - 7.1.1.2 Power Plants: Diaphragm Hydrogen Compressor Market - Revenue, 2021-2034 (US$ Million)
- 7.1.2 Oil and Gas
  - 7.1.2.1 Overview
  - 7.1.2.2 Oil and Gas: Diaphragm Hydrogen Compressor Market - Revenue, 2021-2034 (US$ Million)
- 7.1.3 Food and Beverages
  - 7.1.3.1 Overview
  - 7.1.3.2 Food and Beverages: Diaphragm Hydrogen Compressor Market - Revenue, 2021-2034 (US$ Million)
- 7.1.4 Petrochemical and Chemical
  - 7.1.4.1 Overview
  - 7.1.4.2 Petrochemical and Chemical: Diaphragm Hydrogen Compressor Market - Revenue, 2021-2034 (US$ Million)
- 7.1.5 Hydrogen Fuelling Stations
  - 7.1.5.1 Overview
  - 7.1.5.2 Hydrogen Fuelling Stations: Diaphragm Hydrogen Compressor Market - Revenue, 2021-2034 (US$ Million)
- 7.1.6 Hydrogen Storage (Tube Trailers)
  - 7.1.6.1 Overview
  - 7.1.6.2 Hydrogen Storage (Tube Trailers): Diaphragm Hydrogen Compressor Market - Revenue, 2021-2034 (US$ Million)
- 7.1.7 Others
  - 7.1.7.1 Overview
  - 7.1.7.2 Others: Diaphragm Hydrogen Compressor Market - Revenue, 2021-2034 (US$ Million)

8. Diaphragm Hydrogen Compressor Market - Geographical Analysis

8.1 North America
- 8.1.1 North America Diaphragm Hydrogen Compressor Market Overview
- 8.1.2 North America: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
- 8.1.3 North America: Diaphragm Hydrogen Compressor Market - By Segmentation
  - 8.1.3.1 Type
  - 8.1.3.2 End User
- 8.1.4 North America: Diaphragm Hydrogen Compressor Market Breakdown by Countries
  - 8.1.4.1 United States Market
    - 8.1.4.1.1 United States: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.1.4.1.2 United States: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.1.4.1.2.1 Type
      - 8.1.4.1.2.2 End User
  - 8.1.4.2 Canada Market
    - 8.1.4.2.1 Canada: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.1.4.2.2 Canada: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.1.4.2.2.1 Type
      - 8.1.4.2.2.2 End User
  - 8.1.4.3 Mexico Market
    - 8.1.4.3.1 Mexico: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.1.4.3.2 Mexico: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.1.4.3.2.1 Type
      - 8.1.4.3.2.2 End User
8.2 Europe
- 8.2.1 Europe Diaphragm Hydrogen Compressor Market Overview
- 8.2.2 Europe: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
- 8.2.3 Europe: Diaphragm Hydrogen Compressor Market - By Segmentation
  - 8.2.3.1 Type
  - 8.2.3.2 End User
- 8.2.4 Europe: Diaphragm Hydrogen Compressor Market Breakdown by Countries
  - 8.2.4.1 Germany Market
    - 8.2.4.1.1 Germany: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.2.4.1.2 Germany: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.2.4.1.2.1 Type
      - 8.2.4.1.2.2 End User
  - 8.2.4.2 France Market
    - 8.2.4.2.1 France: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.2.4.2.2 France: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.2.4.2.2.1 Type
      - 8.2.4.2.2.2 End User
  - 8.2.4.3 Italy Market
    - 8.2.4.3.1 Italy: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.2.4.3.2 Italy: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.2.4.3.2.1 Type
      - 8.2.4.3.2.2 End User
  - 8.2.4.4 United Kingdom Market
    - 8.2.4.4.1 United Kingdom: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.2.4.4.2 United Kingdom: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.2.4.4.2.1 Type
      - 8.2.4.4.2.2 End User
  - 8.2.4.5 Russia Market
    - 8.2.4.5.1 Russia: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.2.4.5.2 Russia: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.2.4.5.2.1 Type
      - 8.2.4.5.2.2 End User
  - 8.2.4.6 Rest of Europe Market
    - 8.2.4.6.1 Rest of Europe: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.2.4.6.2 Rest of Europe: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.2.4.6.2.1 Type
      - 8.2.4.6.2.2 End User
8.3 Asia Pacific
- 8.3.1 Asia Pacific Diaphragm Hydrogen Compressor Market Overview
- 8.3.2 Asia Pacific: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
- 8.3.3 Asia Pacific: Diaphragm Hydrogen Compressor Market - By Segmentation
  - 8.3.3.1 Type
  - 8.3.3.2 End User
- 8.3.4 Asia Pacific: Diaphragm Hydrogen Compressor Market Breakdown by Countries
  - 8.3.4.1 Australia Market
    - 8.3.4.1.1 Australia: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.3.4.1.2 Australia: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.3.4.1.2.1 Type
      - 8.3.4.1.2.2 End User
  - 8.3.4.2 China Market
    - 8.3.4.2.1 China: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.3.4.2.2 China: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.3.4.2.2.1 Type
      - 8.3.4.2.2.2 End User
  - 8.3.4.3 India Market
    - 8.3.4.3.1 India: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.3.4.3.2 India: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.3.4.3.2.1 Type
      - 8.3.4.3.2.2 End User
  - 8.3.4.4 Japan Market
    - 8.3.4.4.1 Japan: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.3.4.4.2 Japan: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.3.4.4.2.1 Type
      - 8.3.4.4.2.2 End User
  - 8.3.4.5 South Korea Market
    - 8.3.4.5.1 South Korea: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.3.4.5.2 South Korea: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.3.4.5.2.1 Type
      - 8.3.4.5.2.2 End User
  - 8.3.4.6 Rest of Asia Pacific Market
    - 8.3.4.6.1 Rest of Asia Pacific: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.3.4.6.2 Rest of Asia Pacific: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.3.4.6.2.1 Type
      - 8.3.4.6.2.2 End User
8.4 Middle East and Africa
- 8.4.1 Middle East and Africa Diaphragm Hydrogen Compressor Market Overview
- 8.4.2 Middle East and Africa: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
- 8.4.3 Middle East and Africa: Diaphragm Hydrogen Compressor Market - By Segmentation
  - 8.4.3.1 Type
  - 8.4.3.2 End User
- 8.4.4 Middle East and Africa: Diaphragm Hydrogen Compressor Market Breakdown by Countries
  - 8.4.4.1 South Africa Market
    - 8.4.4.1.1 South Africa: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.4.4.1.2 South Africa: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.4.4.1.2.1 Type
      - 8.4.4.1.2.2 End User
  - 8.4.4.2 Saudi Arabia Market
    - 8.4.4.2.1 Saudi Arabia: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.4.4.2.2 Saudi Arabia: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.4.4.2.2.1 Type
      - 8.4.4.2.2.2 End User
  - 8.4.4.3 United Arab Emirates Market
    - 8.4.4.3.1 United Arab Emirates: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.4.4.3.2 United Arab Emirates: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.4.4.3.2.1 Type
      - 8.4.4.3.2.2 End User
  - 8.4.4.4 Rest of Middle East and Africa Market
    - 8.4.4.4.1 Rest of Middle East and Africa: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.4.4.4.2 Rest of Middle East and Africa: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.4.4.4.2.1 Type
      - 8.4.4.4.2.2 End User
8.5 South and Central America
- 8.5.1 South and Central America Diaphragm Hydrogen Compressor Market Overview
- 8.5.2 South and Central America: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
- 8.5.3 South and Central America: Diaphragm Hydrogen Compressor Market - By Segmentation
  - 8.5.3.1 Type
  - 8.5.3.2 End User
- 8.5.4 South and Central America: Diaphragm Hydrogen Compressor Market Breakdown by Countries
  - 8.5.4.1 Brazil Market
    - 8.5.4.1.1 Brazil: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.5.4.1.2 Brazil: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.5.4.1.2.1 Type
      - 8.5.4.1.2.2 End User
  - 8.5.4.2 Argentina Market
    - 8.5.4.2.1 Argentina: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.5.4.2.2 Argentina: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.5.4.2.2.1 Type
      - 8.5.4.2.2.2 End User
  - 8.5.4.3 Rest of South and Central America Market
    - 8.5.4.3.1 Rest of South and Central America: Diaphragm Hydrogen Compressor Market Revenue and Forecasts, 2021-2034 (US$ Million)
    - 8.5.4.3.2 Rest of South and Central America: Diaphragm Hydrogen Compressor Market - By Segmentation
      - 8.5.4.3.2.1 Type
      - 8.5.4.3.2.2 End User

9. Diaphragm Hydrogen Compressor Market Industry Landscape

10. Diaphragm Hydrogen Compressor Market - Key Company Profiles

10.1 Atlas Copco AB
- 10.1.1 Key Facts
- 10.1.2 Business Description
- 10.1.3 Products and Services
- 10.1.4 Financial Overview
- 10.1.5 SWOT Analysis
- 10.1.6 Key Developments
10.2 Burckhardt Compression AG
- 10.2.1 Key Facts
- 10.2.2 Business Description
- 10.2.3 Products and Services
- 10.2.4 Financial Overview
- 10.2.5 SWOT Analysis
- 10.2.6 Key Developments
10.3 Fluitron, Inc.
- 10.3.1 Key Facts
- 10.3.2 Business Description
- 10.3.3 Products and Services
- 10.3.4 Financial Overview
- 10.3.5 SWOT Analysis
- 10.3.6 Key Developments
10.4 Gardner Denver Nash, LLC
- 10.4.1 Key Facts
- 10.4.2 Business Description
- 10.4.3 Products and Services
- 10.4.4 Financial Overview
- 10.4.5 SWOT Analysis
- 10.4.6 Key Developments
10.5 Howden, A Chart Industries Company
- 10.5.1 Key Facts
- 10.5.2 Business Description
- 10.5.3 Products and Services
- 10.5.4 Financial Overview
- 10.5.5 SWOT Analysis
- 10.5.6 Key Developments
10.6 HAUG Sauer Kompressoren AG
- 10.6.1 Key Facts
- 10.6.2 Business Description
- 10.6.3 Products and Services
- 10.6.4 Financial Overview
- 10.6.5 SWOT Analysis
- 10.6.6 Key Developments
10.7 NEUMAN & ESSER GROUP
- 10.7.1 Key Facts
- 10.7.2 Business Description
- 10.7.3 Products and Services
- 10.7.4 Financial Overview
- 10.7.5 SWOT Analysis
- 10.7.6 Key Developments
10.8 Hydro-Pac, Inc.
- 10.8.1 Key Facts
- 10.8.2 Business Description
- 10.8.3 Products and Services
- 10.8.4 Financial Overview
- 10.8.5 SWOT Analysis
- 10.8.6 Key Developments
10.9 Lenhardt & Wagner GmbH
- 10.9.1 Key Facts
- 10.9.2 Business Description
- 10.9.3 Products and Services
- 10.9.4 Financial Overview
- 10.9.5 SWOT Analysis
- 10.9.6 Key Developments
10.10 PDC Machines Inc.
- 10.10.1 Key Facts
- 10.10.2 Business Description
- 10.10.3 Products and Services
- 10.10.4 Financial Overview
- 10.10.5 SWOT Analysis
- 10.10.6 Key Developments

11. Appendix

11.1 Glossary
11.2 Research Methodology and Approach
- 11.2.1 Secondary Research
- 11.2.2 Primary Research
- 11.2.3 Market Estimation Approach
  - 11.2.3.1 Supply Side Analysis
  - 11.2.3.2 Demand Side Analysis
- 11.2.4 Research Assumptions and Limitations
- 11.2.5 Currency Conversion
11.3 About The Insight Partners
11.4 Market Intelligence Cloud